10-13 YAMAHA YZ450F: UNI Multi-Stage Competition Air Filter Uni Multi-Stage Competition Air Filters are unsurpassed in airflow, dirt stopping and overall performance. And they produce more horsepower and more torque than any other air filter. Uni&#39;s revolutionary two stage air filter is the only filter that comes apart for maximum airflow and ultimate cleaning.Traps dirt and dust in 2 layers of foam.The large pore, pre-filter captures the bigger particles.The small pore, inner filter preven